in theory you are right. You could plug the output of the PS2 into the TV in on a graphics card. However, unless this is to save having both a monitor and a tv in the room its pretty pointless. You would not gain an increased resolution because
a: the ps2 wouldn't be able to output a higher resolution than what the game was origionally intended for
b: the playstation would still think it was outputing to a TV so its resolution would remain static.